Plasma display panel

ABSTRACT

A plasma display panel has a stable addressing characteristic, no dielectric breakdown, and high reliability. Data electrodes ( 10 ), first dielectric layer ( 17 ) for covering them, priming electrodes ( 15 ), and second dielectric layer ( 18 ) for covering them are sequentially formed on back substrate ( 2 ). Slotted parts ( 10   a ) are formed in a part of each data electrode ( 10 ). Thus, data electrodes ( 10 ) are prevented from deforming during the manufacturing, and dielectric voltage between data electrodes ( 10 ) and priming electrodes ( 15 ) is improved.

TECHNICAL FIELD

The present invention relates to a plasma display panel used in awall-hanging television or a large monitor.

BACKGROUND ART

An alternating-current surface discharge type plasma display panel(hereinafter referred to as “PDP”) typical as an alternating-current(AC) type plasma display panel has the following configuration. Theconfiguration has a front substrate formed of glass substrate thatperforms surface discharge and is formed by arranging scan electrodesand sustain electrodes, and a back substrate formed of glass substratehaving arranged data electrodes. The front substrate and the backsubstrate are faced to each other in parallel so that the scanelectrodes and sustain electrodes form a matrix in combination with thedata electrodes and discharge space is formed in a clearance. The outerperipheries of the front substrate and back substrate are sealed by asealant such as glass frit. Discharge cells partitioned by barrier ribsare disposed between the substrates, and phosphor layers are formed incell spaces between the barrier ribs. The PDP having such aconfiguration generates an ultraviolet ray with gas discharge, and emitslight by exciting phosphor of each color with the ultraviolet ray,thereby performing color display.

The PDP divides one field time period into a plurality of subfields, andis driven by combination of the subfields at which light is emitted,thereby performing gradation display. Each subfield is formed of aninitialization time period, an addressing time period, and a sustainingtime period. For displaying image data, different signal waveforms areapplied to each electrode in the initialization time period, theaddressing time period, and the sustaining time period, respectively.

In the initialization time period, for example, positive pulse voltageis applied to all scan electrodes, and required wall charge isaccumulated on a protective film and the phosphor layer. The protectivefilm is disposed on a dielectric layer for covering the scan electrodesand the sustain electrodes.

In the addressing time period, negative scan pulses are sequentiallyapplied to all scan electrodes to perform scan. When the positive datapulses are applied to the data electrodes during scan of the scanelectrodes in a case having display data, discharge occurs between thescan electrodes and the data electrodes, and wall charge is formed onthe protective film on the scan electrodes.

In the subsequent sustaining time period, a voltage sufficient forkeeping the discharge between the scan electrodes and the sustainelectrodes is applied for a certain period. Thus, discharge plasma isgenerated between the scan electrodes and the sustain electrodes, andthe phosphor layer is excited to emit light for a certain period. In thedischarge space where the data pulse is not applied in the addressingtime period, the discharge does not occur and excitation or lightemission does not occur in the phosphor layer.

Such a PDP has a problem where a long delay occurs in the discharge inthe addressing time period and the addressing operation becomesunstable, or a problem where the addressing time is set long forperfectly performing the addressing operation and the time required forthe addressing time period excessively increases. For handling theseproblems, PDPs where an auxiliary discharge electrode is disposed on thefront substrate and a priming discharge caused by the in-plane auxiliarydischarge on the front substrate side reduces the discharge delay, anddriving methods of the PDPs are disclosed in Japanese Patent UnexaminedPublication No. 2001-195990 and Japanese Patent Unexamined PublicationNo. 2002-297091, for example.

When the definition is improved and the number of lines is increased inthese PDPs, however, the time required for the addressing time periodfurther increases, hence the time required for the sustaining timeperiod must be decreased, and the luminance is hardly secured at highdefinition, disadvantageously. Also when xenon (Xe) partial pressure isincreased for achieving high luminance and high efficiency, thedischarge starting voltage increases, the discharge delay increases, andthe addressing characteristic degrades, disadvantageously. Theaddressing characteristic is largely affected by the process, decease ofthe discharge delay in addressing and reduction of the addressing timeare required.

There are the following problems associated with the requirement. Inother words, the conventional PDP that performs the priming discharge inthe front substrate cannot sufficiently reduce the discharge delay inaddressing, has small operation margin in the auxiliary discharge, orcauses false discharge to destabilize the operation, disadvantageously.The auxiliary discharge is formed in the plane of the front substrate,so that priming particles more than required for priming are supplied toan adjacent discharge cell, and crosstalk occurs.

The present invention addresses the above-mentioned problems, andprovides a PDP that can reduce the discharge delay in addressing andstabilize the discharge characteristic, and has high reliability.

SUMMARY OF THE INVENTION

A PDP of the present invention has the following elements:

-   -   a first electrode and a second electrode that are disposed in        parallel on a first substrate;    -   a third electrode disposed in the direction orthogonal to the        first electrode and the second electrode and on a second        substrate facing the first substrate through a discharge space;    -   a fourth electrode disposed on the second substrate, in parallel        with the first electrode and second electrode, and closer to the        first electrode and second electrode than the third electrode;    -   a plurality of main discharge cells formed of the first        electrode, second electrode, and third electrode; and    -   a barrier rib formed on the second substrate so as to partition        a plurality of priming discharge cells formed of the fourth        electrode and one of the first electrode and second electrode.        The third electrode is covered with a first dielectric layer,        the fourth electrode is disposed on the first dielectric layer,        and the third electrode has a slotted part.

This configuration can realize a PDP where the discharge characteristicis stabilized by certainly performing the priming discharge that canreduce the discharge delay in addressing. This configuration can alsorealize a PDP where dielectric breakdown does not occur between thethird electrode and the fourth electrode and has high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a PDP in accordance with an exemplaryembodiment of the present invention.

FIG. 2 is a schematic plan view of an electrode array on a frontsubstrate side of the PDP.

FIG. 3 is a schematic perspective view of a back substrate side of thePDP.

FIG. 4 is a waveform diagram showing one example of a driving waveformfor driving the PDP.

FIG. 5 is a flow diagram of a manufacturing process of the backsubstrate of the PDP.

FIG. 6 is a perspective view showing a shape of a data electrode inaccordance with the first exemplary embodiment of the present invention.

FIG. 7 is a perspective view showing a shape of a data electrode inaccordance with the second exemplary embodiment of the presentinvention.

FIG. 8 is a perspective view showing a shape of a data electrode inaccordance with the third exemplary embodiment of the present invention.

FIG. 9 is a perspective view showing a shape of a conventional dataelectrode.

FIG. 10 is a sectional view of a PDP using the conventional dataelectrode.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A PDP in accordance with an exemplary embodiment of the presentinvention will be described hereinafter with reference to the followingdrawings.

First Exemplary Embodiment

FIG. 1 is a sectional view showing a PDP in accordance with an exemplaryembodiment of the present invention. FIG. 2 is a schematic plan view ofan electrode array on the side of a front substrate as a firstsubstrate. FIG. 3 is a schematic perspective view of the side of a backsubstrate as a second substrate.

As shown in FIG. 1, glass-made front substrate 1 as the first substrateand glass-made back substrate 2 as the second substrate are faced toeach other through discharge space 3, neon (Ne) and xenon (Xe) as gasthat emits ultraviolet rays by discharge are filled into discharge space3. Band-like electrode groups are disposed in parallel on frontsubstrate 1. Each of the electrode groups is covered with frontsubstrate dielectric layer 4 and protective film 5 and has a pair ofscan electrode 6 as a first electrode and sustain electrode 7 as asecond electrode. Scan electrode 6 and sustain electrode 7 are formed oftransparent electrodes 6 a and 7 a and metal buses 6 b and 7 b. Metalbuses 6 b and 7 b are formed so as to overlie transparent electrodes 6 aand 7 a and are made of silver (Ag) or the like for improvingconductivity. As shown in FIG. 1 and FIG. 2, scan electrodes 6 andsustain electrodes 7 are arranged alternately by two, namely in theorder of scan electrode 6—scan electrode 6—sustain electrode 7—sustainelectrode 7 and so on. Light absorbing layers 8 for improving contrastin light emission are disposed between two adjacent scan electrodes 6and between two adjacent sustain electrodes 7. Auxiliary electrode 9 isdisposed on light absorbing layer 8 between two adjacent scan electrodes6, and is connected to one of adjacent scan electrodes 6 in anon-display part (end) of the PDP.

As shown in FIG. 1 and FIG. 3, a plurality of band-like data electrodes10 as third electrodes are disposed on back substrate 2, in parallelwith each other, and in the direction orthogonal to scan electrodes 6and sustain electrodes 7. Each data electrode 10 has slotted parts 10 aas shown in FIG. 3 and FIG. 6. First dielectric layer 17 is formed onback substrate 2 so as to cover data electrodes 10. Priming electrodes15 as the fourth electrodes are formed in parallel with auxiliaryelectrodes 9, at positions corresponding to auxiliary electrodes 9disposed on front surface 1, and on first dielectric layer 17. Seconddielectric layer 18 is formed on first dielectric layer 17 so as tocover priming electrodes 15. Barrier ribs 11 for partitioning aplurality of discharge cells formed of scan electrodes 6, sustainelectrodes 7, and data electrodes 10 are formed on second dielectriclayer 18. Each barrier rib 11 has the following elements:

-   -   longitudinal wall part 11 a extending in the direction        orthogonal to scan electrodes 6 and sustain electrodes 7 that        are disposed on front surface 1, namely in the direction        parallel with data electrodes 10; and    -   lateral wall part 11 b that is orthogonal to longitudinal wall        part 11 a, forms main discharge cells 12, and forms clearances        13 partially defining a priming electrode cell between main        discharge cells 12.        Phosphor layers 14 are formed on main discharge cells 12.

In FIG. 3, clearances 13 on back substrate 2 are continuously formed inthe direction orthogonal to data electrodes 10, and form primingdischarge cells 16. In each priming discharge cell 16, data electrodes10 are covered with first dielectric layer 17, priming electrode 15 isformed on first dielectric layer 17, and second dielectric layer 18 isformed on priming electrode 15. Priming electrode 15 is closer toprotective film 5 of front substrate 1 than data electrodes 10, andhence has a discharge distance that is shorter than that between frontsubstrate 1 of main discharge cell 12 and data electrode 10 by thicknessof first dielectric layer 17.

Next, a method of displaying image data on the PDP is described. In adriving method of the PDP, one field period is divided into a pluralityof subfields having a weight of light emitting period in binarynotation, and gradation display is performed by combination of thesubfields for emitting light. Each subfield is formed of aninitialization time period, an addressing time period, and a sustainingtime period. FIG. 4 is a waveform diagram showing one example of adriving waveform for driving the PDP of the present embodiment of thepresent invention. Firstly, in initialization time period, in thepriming discharge cell (priming discharge cell 16 in FIG. 1) havingpriming electrode Pr (priming electrode 15 in FIG. 1), positive pulsevoltage is applied to all scan electrodes Y (scan electrodes 6 in FIG.1), and the initialization is performed between the auxiliary electrode(auxiliary electrode 9 in FIG. 1) and priming electrode Pr. In thesubsequent addressing time period, positive voltage is always applied topriming electrode Pr. Thus, when scan pulse SP_(n) is applied to scanelectrode Y_(n) in the priming discharge cell, priming discharge occursbetween priming electrode Pr and the auxiliary electrode, and primingparticles are supplied to the main discharge cell (main discharge cell12 in FIG. 1). Next, scan pulse SP_(n+1) is applied to scan electrodeY_(n+1) in the n+1-th main discharge cell. Since the priming dischargeoccurs just before the application, the priming particles are alreadysupplied and hence the discharge delay in the next addressing time canbe reduced. Only driving sequence of one field has been described;however, the operation principle in the other subfield is similar. Inthe driving waveform shown in FIG. 4, positive voltage is applied topriming electrode Pr in the addressing time period, thereby certainlycausing the above-mentioned operation. The applied voltage to primingelectrode Pr in the addressing time period is preferably set larger thandata voltage value applied to data electrode D (data electrode 10 inFIG. 1).

In this configuration, each priming electrode 15 is formed on firstdielectric layer 17 in each priming discharge cell 16. Therefore, whenfirst dielectric layer 17 is appropriately formed, the dielectricvoltage between data electrode 10 and priming electrode 15 can besecured by first dielectric layer 17. The priming discharge and addressdischarge can be stably generated. First dielectric layer 17 disposed inpriming discharge cell 16 makes the height of the discharge space ofpriming discharge cell 16 lower than the height of the discharge spaceof main discharge cell 12. Thus, priming discharge in main dischargecell 12 corresponding to scan electrode 6 connected to auxiliaryelectrode 9 can be stably generated before the address discharge in maindischarge cell 12, and the discharge delay in main discharge cell 12 canbe reduced.

FIG. 5 is a flow diagram of a manufacturing process of the backsubstrate of the PDP in accordance with the present embodiment of thepresent invention. The manufacturing process of the back substrate ofthe PDP is described hereinafter with reference to FIG. 5.

A back glass substrate as back substrate 2 is prepared in step 1. Next,data electrodes 10 are formed in step 2. Silver (Ag) paste is applied todata electrodes 10, and the silver (Ag) line is then formed by aphoto-lithograph method. After that, data electrodes 10 are burned to besolidified and formed. Each data electrode 10 has square holes asslotted parts 10 a as shown in FIG. 3 and FIG. 6, and has a laddershape. Forming data electrode 10 in the ladder shape can release an airbubble generated during the burning of data electrode 10 from the squareholes (slotted parts 10 a), so that the air bubble can be prevented fromdeforming data electrode 10. Side surface parts of slotted parts 10 aare formed to increase the area for releasing the air bubble, and thedeformation of data electrode 10 can be effectively prevented.

FIG. 9 is a perspective view showing a shape of conventional dataelectrode 100. FIG. 10 is a sectional view of a PDP using the dataelectrode 100. When data electrode 100 has a strip shape as shown inFIG. 9, namely a plane shape in the longitudinal direction of theelectrode, there are the following problems. A foreign matter or organicmatter existing between data electrode 100 and back glass substrate 102generates air bubble in a burning process of data electrode 100. Sincedata electrode 100 is plane, the air bubble cannot separate upward andhence the air bubble presses up data electrode 100. Therefore, dataelectrode 100 is pressed by air bubble 101 to be deformed as shown inFIG. 10, and insulation distance between data electrode 100 and primingelectrode 15 cannot be always kept.

While, in embodiment 1 of the present invention shown in FIG. 6, thegenerated air bubble separates upward through the square holes ofslotted parts 10 a formed in the longitudinal direction of dataelectrode 10, and data electrode 10 does not deform during burning. Thedistance between data electrode 10 and priming electrode 15 can betherefore kept suitable, the cause of the dielectric breakdown isremoved, and a PDP having high reliability can be realized. Since dataelectrode 10 is formed in the ladder shape as shown in FIG. 6, the wholeconduction in the longitudinal direction can be secured even when theelectrode part is partially disconnected, and a PDP having highreliability can be realized.

Next, first dielectric layer 17 is formed in step 3. As the material offirst dielectric layer 17, a ZnO—B₂O₃—SiO₂ based mixture, aPbO—B₂O₃—SiO₂ based mixture, a PbO—B₂O₃—SiO₂—Al₂O₃ based mixture, aPbO—ZnO—B₂O₃—SiO₂ based mixture, or a Bi₂—O₃—B₂O₃—SiO₂ based mixture isused. In the present embodiment, the PbO—B₂O₃—SiO₂ based mixture havingthe composition of PbO: 65 to 70 wt %, B₂O₃: 5 wt %, and SiO₂: 25 to 30wt % is used. The material of first dielectric layer 17 is deformed to apaste form, and is applied to data electrode 10. The applying method isnot especially limited, a publicly known applying and printing methodcan be used. For example, a roll coating method, a slit die coatingmethod, a doctor blade method, a screen printing method, and an offsetprinting method are used. In the present embodiment, the applyingthickness of the paste of first dielectric layer 17 depends on thecontent of inorganic components in the paste, but is preferably 5 to 40μm. By setting the applying thickness of the paste of first dielectriclayer 17 at 5 μm or thicker, the unevenness of the electrode layer afterburning can be moderated. Then, the paste of first dielectric layer 17is burned and solidified.

Next, priming electrodes 15 are formed in step 4. The forming methodthereof is substantially similar to that of data electrodes 10 in step2, and silver (Ag) paste is burned.

Next, second dielectric layer 18 is formed in step 5. The forming methodthereof is substantially similar to that of first dielectric layer 17 instep 3. In a method similar to the forming method of first dielectriclayer 17, burning and solidification are performed after application.

Next, barrier ribs 11 and phosphor layers 14 are formed in step 6.Photosensitive paste that contains glass components and photosensitiveorganic components is applied and dried, and then a pattern oflongitudinal wall parts 11 a and lateral wall parts 11 b is formed usinga photo process or the like. Here, wall parts 11 a and 11 b form thespaces of main discharge cells 12, the spaces of priming discharge cells16, and the spaces of clearances 13. Phosphor layers 14 of R, G and Bare applied and filled into main discharge cells 12. Barrier ribs 11 andphosphor layers 14 are simultaneously burned and solidified, therebyforming final barrier ribs 11 and phosphor layer s14.

Back substrate 2 is finished by the above-mentioned processes (step 7).

Second Exemplary Embodiment

FIG. 7 is a perspective view showing a shape of data electrode 10 inaccordance with the second exemplary embodiment of the presentinvention. In the second exemplary embodiment, slotted parts 10 a indata electrode 10 are circular or elliptic holes. The configurationexcept for slotted parts 10 a is similar to that of embodiment 1.

Forming slotted parts 10 a in data electrode 10 as the circular orelliptic holes produces the following advantage. In other words, thoughspace for releasing the air bubble is narrower than that in the caseusing square holes, stress concentration can be suppressed because theholes of slotted parts 10 a have no sharp edge, and torsion or chamberdue to heating can be reduced. As a result, a PDP having high reliableand no cause of dielectric breakdown in addition to the advantagedescribed in embodiment 1 can be realized.

Third Exemplary Embodiment

FIG. 8 is a perspective view showing a shape of data electrode 10 inaccordance with the third exemplary embodiment of the present invention.In the third exemplary embodiment, slotted parts 10 a in data electrode10 have a shape where side parts are alternately notched in thelongitudinal direction of data electrode 10. The configuration exceptfor slotted parts 10 a is similar to that of embodiment 1. Formingslotted parts 10 a in this shape allows the hole area, namely the spacefor releasing the air bubble, to be enlarged, and largely suppresses thedeformation of data electrode 10 due to the air bubble. A PDP havinghigh reliable and no cause of dielectric breakdown can be realized.

In the manufacturing processes of exemplary embodiments 1 to 3 of thepresent invention, data electrodes 10, first dielectric layer 17,priming electrodes 15, second dielectric layer 18, barrier ribs 11, andphosphor layers 14 are sequentially applied, burned, and solidified.However, for simplifying the processes, the layers may be burned andsolidified in a lump after sequentially application. In this case, theair bubble generated from data electrodes 10 disposed in the lowestlayer must be further sufficiently released. However, in the exemplaryembodiments of the present invention, the air bubble can be furthereffectively released, hence the shape of data electrodes 10 can bestabilized, and the dielectric voltage can be improved.

In the exemplary embodiments of the present invention, slotted parts 10a are disposed in each data electrode 10 on back substrate 2 to preventthe deformation of data electrode 10 during burning. However, thismethod can be used when metal buses 6 b and 7 b are formed on frontsubstrate 1. In other words, slotted parts are disposed in metal buses 6b and 7 b to prevent the deformation thereof during burning, therebyimproving the withstanding voltage characteristic by dielectric layer 4on the front substrate.

INDUSTRIAL APPLICABILITY

The present invention can provide a PDP where certain priming dischargeis allowed, dielectric voltage between the data electrode and thepriming electrode is secured, and reliability is high. The PDP istherefore used in a large-screen display device or the like.

1. A plasma display panel comprising: a first electrode and a secondelectrode that are disposed in parallel on a first substrate; a thirdelectrode disposed in a direction orthogonal to the first electrode andthe second electrode and on a second substrate that faces the firstsubstrate through a discharge space; a fourth electrode disposed on thesecond substrate, in parallel with the first electrode and the secondelectrode, and closer to the first electrode and the second electrodethan the third electrode; a plurality of main discharge cells formed ofthe first electrode, the second electrode, and the third electrode; anda barrier rib formed on the second substrate so as to partition aplurality of priming discharge cells formed of the fourth electrode andone of the first electrode and second electrode, wherein the thirdelectrode is covered with a first dielectric layer, the fourth electrodeis disposed on the first dielectric layer, and the third electrode has aplurality of slotted parts in a longitudinal direction of the thirdelectrode.
 2. The plasma display panel according to claim 1, wherein thethird electrode has the plurality of slotted parts in a longitudinaldirection of the third electrode, and hence has a ladder shape.
 3. Theplasma display panel according to claim 1, wherein the slotted parts aresquare holes.
 4. The plasma display panel according to claim 1, whereinthe slotted parts are circular or elliptic holes.
 5. The plasma displaypanel according to claim 1, wherein the slotted parts are formed byalternately notching side parts in a longitudinal direction of the thirdelectrode.
 6. The plasma display panel according to claim 2, wherein theslotted parts are square holes.
 7. The plasma display panel according toclaim 2, wherein the slotted parts are circular or elliptic holes.